1. Field of the Invention
The present invention relates to a clump-forming hygiene granulate, particularly an animal litter, preferably a cat litter, and to a method for its production.
2. Description of the Related Art
In the case of hygiene granulate, a distinction is made essentially between two different types, namely between light-weight litters and clump-forming litters. Light-weight litters have a great absorption capacity for liquids, above all urine, and good odor binding with low bulk density. The consistency of the light-weight litter does not change when it absorbs liquid. Light-weight litters consist, for example, of mineral grains that cannot swell, for example composed of autoclaved aerated concrete. In contrast to light-weight litters, clump-forming litters form firm agglomerates with the added liquid (“clumps”), which can be individually removed. As a result, material consumption and odor formation are less. Above all, clay minerals capable of swelling, particularly bentonite, and/or hydrocolloids are used as clump-forming materials. For this reason, clump-forming litters generally have a greater bulk density and are more expensive than light-weight litter. To reduce the bulk density of clump-forming hygiene granulates, it is furthermore known to use granules that consist of a core composed of material that cannot swell, for example autoclaved aerated concrete, which has a mantle of clump-forming material.
For example, a hygiene granulate is evident from DE 198 39 240 A1, which has granules that each have a core of calcium silicate hydrate material. The core has a surface coating composed of a substance that is capable of swelling and is sticky when moisture is added. This material is methyl cellulose or carboxymethyl cellulose, for example. For the production of the hygiene granulate, a thin coating of the dry substance that is capable of swelling and sticky when moisture is added is powdered onto the moist cores of calcium silicate hydrate material.
DE 198 43 887 C5 discloses a hygiene granulate on the basis of calcium silicate hydrate and bentonite, which has pelletized granules having a two-layer structure with a core composed of a primary pellet and a mantle. The core consists of a mixture of 85 to 95 mass-% calcium silicate hydrate material and 5 to 15 mass-% fine-particle bentonite, and the mantle has a mixture of fine-particle clay mineral capable of swelling and fine-particle calcium silicate hydrate. In this connection, the mixture has 35-65 mass-% calcium silicate hydrate material and 65-35 mass-% bentonite, and the fine-particle calcium silicate hydrate material has grain sizes of 1 to 100 μm. The primary pellet has grain sizes of 0.5-3.5 mm, and the granules of the granulate have grain sizes of 2-5 mm.
DE 10 2008 048 736 B4 discloses an animal litter composed of a porous carrier material that is coated with a clay mineral, where a layer of a non-ionic hydrocolloid is present between the carrier material and the clay mineral. The production of the animal litter takes place by moistening the carrier material with an aqueous solution that contains non-ionic hydrocolloid, and mixing the moistened carrier material with clay mineral. Subsequently, the mixture obtained is dried. The animal litter of DE 10 2008 048 736 B4 does form firm clumps at pH=6, but at other pH values the clumps are very sticky and smeary. The pH of cat urine can vary, however, for example due to illness. Then there is the risk that the sticky clumps become caught in the animals' fur.